1. Technical Field
This invention relates to friction clutches and transmissions for large automotive vehicles.
2. Background Art
The use and function of a clutch brake are well known in the art. The purpose of a clutch brake is to aid in gear shifting in non-synchronized transmissions.
The clutch brake, which has a generally flat and annular shape, is splined onto the transmission input shaft in between the release bearing mechanism and transmission. Upon disengagement of the main clutch of the vehicle, the clutch brake retards and stops the rotation of the driven shaft so that a smooth gear shifting operation may be performed.
Because of its relatively small size and the torsional forces to which it is subjected during use, replacement of the clutch brake is often required prior to the replacement of the main clutch and transmission.
A number of clutch brake designs are in use. All of the known designs, however, have some disadvantages, mostly related to their assembly, installation and removal. Categorizing these known designs according to their installation procedure, clutch brakes are available in three versions: a unitary annular assembly, an assembly with two separate mating halves, and a hinged assembly.
The unitary assembly, although inexpensive, is replaced by partially disassembling the clutch, disassembling the transmission, or by fracturing the clutch brake in two places to allow its removal. All three options are costly, the last one being potentially even dangerous.
Clutch brakes that comprise two mating halves assembled and secured to form an annular assembly are exemplified by the clutch brakes shown in U.S. Pat. No. 4,512,450 to Babcock, U.S. Pat. No. 5,031,739 Flotow et al. and U.S. Pat. No. 5,076,406 to Gregory et al.
U.S. Pat. No. 4,512,450 to Babcock discloses a clutch brake comprising a pair of initially separate semi-annular sections having radial interlocking teeth, which permit the clutch brake to be assembled as it is installed on the driven shaft. The halves are placed along the periphery of the shaft with the tangs located in keyways along the shaft. The halves are then assembled by engaging the interlocking teeth, and then spot welding the components together. Alternatively, pins are assembled into one half of the clutch brake and then are pressed into mating holes in the other half of the clutch brake to secure the components together.
U.S. Pat. No. 5,031,739 to Flotow, et al. discloses a clutch brake formed from a pair of identically shaped semi-annular sections. Each section has circumferentially extending protrusions located at either end, an outer protrusion at one end of the section and an inner protrusion at the other end of the section. Each outer protrusion has a radial clearance hole, and each inner protrusion has a radial threaded hole. In assembly, the sections are placed independently over the shaft. Threaded fasteners are inserted radially into the clearance holes and threaded into the threaded holes to secure the components together. The fasteners form the tangs for securing the brake to the shaft.
U.S. Pat. No. 5,076,406 to Gregory, et al. discloses a clutch brake of two interlocking parts adapted to fit together. In a preferred form, the clutch brake incorporates first and second interlocking U-shaped parts which together define a central aperture to engage a clutch shaft. The second part is radially inserted via a tongue and groove into the first part to couple the two parts together. A bowed spring has a pair of ends which spread apart atop the second interlocking part by application of a radial force sufficient to partially flatten the bowed portion. A pair of aligned bores in the first and second parts receive the ends of the spring, thus securing the two parts together. The bowed portion of the spring includes a non-threaded aperture, and the second part includes a threaded aperture directly under the non-threaded spring aperture. For retaining the bowed portion of the spring in a deflected condition and to retain the two parts together, the shaft of a bolt is inserted through the spring aperture and secured within threaded aperture of the second part. Rotation of the bolt head causes a radially inwardly directed force to deflect the bowed portion. The bolt head also operates to retain the spring in a deflected condition.
A clutch brake having a hinged assembly is shown in U.S. Pat. No. 5,285,881 to Lero et al. This patent discloses a clutch brake comprised of at least two arcuate members pivotally connected to each other by means of a rivet or the like and spaced-apart tabs for coupling the arcuate members to the shaft. To install, one of the arcuate members is positioned about the shaft and the second arcuate member then pivoted inward to form a closed annular assembly about the shaft. A second fastening rivet is then installed in the opposite ends of the arcuate members to couple the components together and secure the assembly to the shaft. The force for installing the second rivet may be provided by a tool or by a force created by depressing the clutch pedal.
While a clutch brake is generally simple in its structure and function, the designs of the prior art typically include small pieces that are difficult to work with in the small spaces encountered during installation and/or are difficult to remove safely and without damage to the clutch brake and the adjacent components of the clutch.
Each of the multi-component clutch brakes designs of the prior art requires extensive on-site assembly, as the separate components are assembled together as they are placed over or assembled on the shaft. This on-site assembly is generally cumbersome, in that the assembler must reach through an inspection portion of the bell housing of the transmission approximately 5 inches by 8 inches in size in order to secure the clutch brake along opposite sides of the shaft. Further loose components, such as pins and threaded fasteners may be easily lost during the xe2x80x9cblindxe2x80x9d installation. These loose parts can damage the transmission if left loose in the transmission housing.
Additionally, special installation tools are often required to perform the assembly. Such tools may be unavailable on a remote repair site. Further, such dedicated tools may present significant expense. For example, welding equipment is quite expensive, and may not be readily available or portable.
The prior art also offers a number of interlocking clutch brakes of the type referred to as xe2x80x9creplaceable.xe2x80x9d Most however are relatively expensive to manufacture, and require relatively complex apparatus for their manufacture and use. Several of the devices are easily installed, but difficult to remove after installation. The clutch brake described in Babcock et al., for example, requires the use of spot welding for installation of the clutch brake on a clutch shaft, but subsequently requires the use of a torch to cut the used clutch brake from the shaft. A more convenient system would avoid any use of welding, and would preferably require only the use of a single hand-operated tool for both assembly and disassembly.
Accordingly, it is an object of the present invention to provide a clutch brake assembly that is easily installed on and removed from the transmission input shaft without damage to the clutch brake.
It is a further object of the present invention to provide a clutch brake that may be installed or removed without the use of special tools and, more specifically, may be installed or removed manually.
It is an additional object to provide a clutch brake assembly that does not include small parts or pieces that may be difficult to manipulate in the confined areas encountered in its installation of the clutch brakes.
These objects, as well as others that will become apparent upon reference to following detailed description and accompanying drawings, are achieved by a clutch brake adapted to be connected to a rotary shaft having a pair of radially opposed keyways in which the clutch brake has first and second arcuate members, each with first ends and second ends. A pivot connector couples the first end of each arcuate member to the other arcuate member so that the arcuate members pivot with respect to each other in a substantially flat, coplanar relationship. Each of the first and second arcuate members includes a projecting tab for engagement with one of the keyways of the shaft. The second ends of each arcuate member includes a complementarily-shaped mating projection to releasably join the second ends of the arcuate members to each other to removably secure the clutch brake to the shaft.
When the clutch brake is closed about the shaft, the two arcuate members are forced out of their coplanar relationship upon the initial engagement of the complementarily-shaped mating projections. When the arcuate members return to their coplanar relationship upon the proper seating of the mating projections, an audible noise is created to indicate to the installer that the clutch brake has been securely attached to the shaft.
In the preferred embodiment, the complementarily-shaped mating projections each have a portion that is inclined away from the second ends of their respective arcuate members and a tab, which seats in a relieved area spaced from the second end.
The pivotal connector may be adapted to permit a minor amount of non-coplanar pivotal movement between the two arcuate members to accommodate the engagement of the complementarily-shaped mating projections. In the preferred embodiment, this is accomplished by having a rivet with a head that is received in a countersunk portion on the first end of one of the arcuate members, with a flexible washer, commonly known as a xe2x80x9cbelleville washer,xe2x80x9d secured to the shaft of the rivet underneath the head.
The second ends of each arcuate member may include an aperture for receiving a rod. When a rod is received in each of the holes, a pair of levers is provided which may be gripped to facilitate the closing of the clutch brake.